title: Expression of PIK3CA, PTEN mRNA and PIK3CA mutations in primary breast cancer: association with lymph node metastases.
abstract: OBJECTIVE
  High activity of the intracellular phosphatidylinositol-3 kinase (PI3K) pathway is common in breast cancer. Here, we explore differences in expression of important PI3K pathway regulators: the activator, phosphatidylinositol-3-kinase catalytic subunit alpha (PIK3CA), and the tumour suppressor, phosphatase and tensin homolog (PTEN), in breast carcinoma tissue and normal breast tissue. Furthermore, we examine whether expression of PIK3CA and PTEN mRNA and occurrence of PIK3CA mutations are associated with lymph node metastases in patients with primary breast cancer.
  
  
  METHODS
  Paired tissue samples of breast carcinoma and normal breast tissue were obtained from 175 breast cancer patients at the time of primary surgery, of these 105 patients were lymph node positive. Expression of PIK3CA and PTEN mRNA was quantified with Quantitative Real Time PCR. Somatic mutations in exon 9 and exon 20 of the PIK3CA gene were identified by genotyping.
  
  
  RESULTS
  Both PIK3CA and PTEN mRNA expression was significantly increased in breast carcinoma tissue compared to normal breast tissue (p = 2 × 10(-11)) and (p < 0.001), respectively. PIK3CA mutations were present in 68 out of 175 patients (39%), but were not associated with PIK3CA expression (p = 0.59). Expression of PIK3CA and PTEN mRNA, and PIK3CA mutations in breast carcinomas were not associated with presence of lymph node metastases.
  
  
  CONCLUSIONS
  The expression of PTEN and PIK3CA mRNA is increased in breast carcinoma tissue compared to normal breast tissue, and PIK3CA mutations are frequent in primary breast carcinoma, however these factors were not associated with lymph node metastases.
authors.affiliation: Department of Clinical Biochemistry, Herlev Hospital, Herlev Ringvej 75, Herlev, 2730 Denmark ; Department of Clinical Biochemistry, Herlev Hospital, Herlev Ringvej 75, Herlev, 2730 Denmark.
authors.forename: Irina
authors.initials: I
authors.lastname: Palimaru
authors.forename: Anja
authors.initials: A
authors.lastname: Brügmann
authors.forename: Marie Kim
authors.initials: MK
authors.lastname: Wium-Andersen
authors.forename: Ebba
authors.initials: E
authors.lastname: Nexo
authors.forename: Boe Sandahl
authors.initials: BS
authors.lastname: Sorensen
keywords: Breast cancer; Lymph node metastases; Mutations; PI3K pathway; PIK3CA; PTEN